I want to live abroad. I am an adult now, but my parents do not agree. If I use my ID card to take the train, will the police find out where I have been?

First of all, to answer your question, the police will check which city you got off the train in. They can also check if you stay in a hotel. They can only check where you live if you rent a house. In some big cities, they can also check if you rent a house. Report to the police. As for why you want to go abroad? Will you go to another place when you become an adult? Nowadays, when you watch the news, aren’t there adults who have been cheated and killed? So there is a reason why your parents are worried about you and won't let you go abroad. Unless you have something to rely on overseas, such as friends and relatives your parents have met, your parents will definitely agree to it!